Reinforced plastic bag and method of making the same



E. KUGLER 3,084,731

REINFORCED PLASTIC BAG AND METHOD OF MAKING THE SAME April 9, 1963 FiledDec. 15, 1959 w MG Z v 1% w ML, x 6 EM United States Patent 3,584,731REINFORCED PLASTIC BAG AND METHOD OF MAKING THE AME Emanuel Kugler, 296Hungry Harbor Road, Valley Stream, NSY. Filed Dec. 15', 1959, Ser. No.859,642 2 Claims. (Cl. 150-11) This invention relates to plastic bagsand the method of making same. More particularly, the invention relatesto reinforced plastic bags of an improved type which are lesssusceptible to failure during use than conventional plastic bagsutilizing an equal amount of material.

it is common practice to form bags from relatively thin plastic materialsuch as polyethylene. Such bags are put to a variety of uses and aremade in a wide variety of sizes from material of varying thicknesses.Since it is possible to form such plastic bags with walls of almost anydesired thicknesses, the wall thickness of a given bag is usuallydetermined by the use to which it is designed to be put. Obviously, itis to the manufacturers advantage to make the bag as thin as possible inorder to use a minimum of material. At the same time the bag must besufficiently thick so that it does not rupture or tear at localizedzones of stress under normal conditions of use. Certain portions of aplastic bag are frequently subjected to considerably greater strain thanother portions thereof. This may be due to the size, weight or shape orcharacter of merchandise which is packaged in the bag, or to otherfactors. For instance, in the case of draw string bags which arefrequently reused by the ultimate consumer, the tubular hems at themouth of the bag which contain the draw strings often tear when a filledbag is carried by the draw strings or following openings or closing ofthe bag a number of times. Likewise, bags into which relatively heavyobjects are put also tear at the bottom margin of the bag. In order toprevent failure of bags under conditions such as these, while at thesame time economizing in the poundage of. material used, it is highlydesirable to provide reinforcement at those portions of a bag which arelikely to be subjected to greater stress than the remainder of the bag.It is also highly desirable to avoid the use of separate reinforcingstrips since the use of such strips complicates the manufacturingprocess, increases the cost appreciably and is not well adapted tocontinuous manufacturing operations. It is an object of the presentinvention to provide an improved plastic bag and process of making samewhich allows attainment of the above objectives in a simple andeflicient manner.

According to a preferred embodiment of one aspect of this invention, aplastic bag is provided which is formed from a single ply piece ofrelatively thin, flexible plastic material such as polyethylene and inwhich the single ply material at one or more localized zones issubstantially thicker than the material forming other portions of thebag. For example, such thicker zones may be a pair of opposed'zones suchas at the mouth and the bottom margin of the bag. Likewise, a thickenedzone may be provided at a desired location on one or both side bagpanels to resist localized strain or abrasion due to the character ofthe article to be packed.

According to a preferred embodiment of another aspect of the invention,plastic bags of the type described above are produced by forming a tubeof plastic material which has at least one longitudinally extendingthickened area of restricted width positioned to correspond to atransversely extending reinforced zone where desired on the finishedbag. Further, a plurality of such thickened areas may be providedcircumferentially spaced from each other to correspond to thickened hemportions of the bags,

3,084,731 Patented Apr. 9, 1963 and if desired, also a predeterminedthickened area of a face panel. This tube is then formed into plasticbags of the type described above so that the thickened areas of the tubefall at the desired zone or zones to be reinforced in each of the bagsmade from such tube.

For a better understanding of the invention reference should be had tothe accompanying drawings which illustrate somewhat diagrammatically abag constructed in accordance with the invention and a method of makingthe same in accordance with the invention.

In the drawings:

FIG. 1 is a plan view of a tube of plastic material made in accordancewith my invention suitable for forming into plastic bags in accordancewith the invention;

FIG. 2 is a cross-sectional view taken at line 22 of FIG. 1, with thetube shown in somewhat collapsed or flattened form;

FIG. 3 is a somewhat diagrammatic sectional view of a portion ofi asuitable arrangement of apparatus for producing the tube shown in FIG.1;

FIG. 4 is a front elevational view of one embodiment of a draw stringbag made from the tube shown in FIG. 1 and constructed in accordancewith the invention;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4; and

FIG. 6 is a view similar to FIG. 5 showing a modification of theinvention.

Referring to the drawings, FIGS. 1 and 2 show a tube 11 of relativelythin, flexible plastic, single ply material such as polyethylene andhaving a pair of longitudinally extending, circumferentially spacedthickened areas 12 and 13. The tube 11 may be formed in any suitablemanner such as by extruding the plastic material through an extrusiondie 15 having an annulus nozzle 16 (FIG. 3) in the manner taught by US.Patent No. 2,720,680. When the tube is formed in accordance with myinvention, the thickened areas 12 and '13 of the tube are easily formedby varying the radial width of the nozzle at 10- calized zones, asindicated at 17 and 18 in FIG. 3. It is readily apparent that thesezones of greater nozzle width determine the thickness of the extrudedtube and that this thickness may, therefore, be varied by varying thethickness of the nozzle width at one of more zones spaced about thecircumference of the die. In accordance with the disclosure in saidpatent, the extruded tube is expanded to a diameter depending upon thewall thickness desired.

FIGS. 4 and 5 show a draw string bag 21 which may be formed in anysuitable manner such as from the tube 11 in the manner described belowand taught in greater detail in my copending application Ser. No.858,659 filed December 10, 1959. As shown in FIGS. 4 and 5, the bag 21is constructed of flexible plastic single ply material such aspolyethylene and has front and back panels 22 and 23 connected togetheralong the bottom margin 24 and side margins 25 and26 of the bag. Opposedtransverse edge portions of the panels 22 and 223 remote from the bottommargin 24 are formed into tubular hems or lips 27 and 28 which form anopen mouth at the upper margin of the bag and are adapted to containdraw strings such as 29 and 30. The draw strings 29 and 30 may be ofsuitable material such as string and may be fastened together outsidethe side margins of the bag as by staples 31 and 32, while the tubularlips 27 and 28 may be formed by folding the edge portions of the panels22 and 23 and sealing as indicated by the seal lines 33 and 34 (FIG. 5).As best shown in FIG. 5, the bottom margin 24 and the tubular hems 27and 28 forming the upper margin of the bag 21 are formed of materialwhich is substantially thicker than material forming other portions ofthe bag. Because of these reinforced upper and lower margins, the. bag21 is able to withstand greater strains at these vulnerable portions ofthe bag than would otherwise be possible without the use ofsubstantially greater amounts of material in making the bag.Furthermore, this reinforcement is obtained without the use of separatereinforcing strips which would greatly complicate the process ofmanufacturing the bag and add considerably to the cost thereof.

As mentioned above, the bag 21 may conveniently be formed from the tube11. This may be accomplished by forming a longitudinal fold along acentral portion of the thickened area 12 as indicated by a fold line 35in FIGS. 1 and 2. The tube 11 is then severed longitudinally along acentral portion of the thickened area 13 as indicated at 36 (FIG. 2') todivide the thickened area 13 into opposed severed portions. Thesesevered portions of the thickened area 13 are then folded and sealedalong the seal lines 33 and 34 to form the tubular hems 27 and 28 in themanner taught by my above mentioned application Ser. No. 858,659. Thetube Ill may then be severed and sealed at bag width intervals alongtransverse seal lines such as 37 and 38 (FIG. 1) to form individual bagssuch as the bag 21. In this way the seal lines 37 and 38 form the sidemargins 25 and 26 of the 'bag 21 while the thickened areas 12 and 13form the upper margin (lips 27 and 28) and lower margin 2% of the bagrespectively. If desired, the fold along the fold line 35 may be agusseted fold so as to produce a bag having a gusseted bottom, margin.It is also, of course, possible to form a bag similar to the bag 21 butWithout the tubular hems merely by omitting the step of folding andsealing the transverse edge portions of the panels 22 and 23.

While the bag 21 has been described as having the upper and lowermargins thereof formed of relatively thicker material than the remainderof the bag, the present invention is equally applicable to situations inwhich it is desired to have only one margin, such as the lower margin orthe mouth of the bag, of thickened material or in which it is desired tohave one or both of the opposite side panels of the bag provided withlocalized thickened zones of material. A bag similar to the bag 21described above may, for instance, be formed with only the tubular lipsof such thickened material by forming -a tube similar to the tube 11 buthaving only one thickened area corresponding to the thickened area 12 ofthe tube 11.

Similarly, a localized thickened zone may be readily provided at anyplace extending transverse the bag width and said zone may be of suchportion of the bag height as desired. For example, where the bag is tobe used to hold a toy or other article having a projection or irregularshape, the bag may be provided with a thickened zone extending acrossone or both side panels so positioned as to reinforce the bag only Whereneeded. Such a modification is shown in FIG. 6 Where the bag isidentical with that shown in FIG. except for an additional localizedreinforcing thickened zone such as 40 on one side panel.

The tube 11 and bag 21 described above, as well as other bags within thescope of the invention, may be formed of any suitable flexible plasticmaterial. Extrudable materials such as polyethylene are especiallysuitable in this respect since bags may then be formed from extrudedtubes in the manner described above. Bags formed of such material mayhave any suitable normal Wall thickness and localized thickened zoneswithin the permissible limits of the extrusion method of making thetubes. 1

While the invention has been described above with reference to certainpreferred embodiments thereof, it will be understood by those skilled inthe art that various changes and modifications are possible withoutdeparting from the spirit and scope of the invention and it is intendedto cover such changes and modifications in the appended claims.

I claim:

1. The method of ma king a tubular drawstring bag, comprising the stepsof forming a substantially cylindrical tube of thin flexible plasticmaterial having a locally thickened area extending longitudinallysubstantially along its length, longitudinally severing said tubesubstantially along the centerline of said thickened area to provide amouth end and oppositely disposed face panels of the bag, said facepanels respectively including opposed edge portions provided by saidsevered thickened area, folding each of said opposed edge portions alongand substantially centrally of its length and attaching the same to itssaid respective face panel to provide complementary tubular hems at saidmouth end of the bag for receiving a drawstring, and sealing said facepanels to gether along longitudinally spaced apart transverse seal linesto form opposed side edges of said bag.

2. The method of making a tubular drawstring bag, comprising the stepsof forming a substantially cylindrical tube of thin flexible plasticmaterial having a pair of locally thickened areas each extendinglongitudinally substantially along its length on diametrically oppositesides of the tube, forming a longitudinally extending fold along thelength of the first of said thickened areas and longitudinally severingsaid tube along substantially the centerline of the second of saidthickened areas to provide a mouth end and oppositely disposed facepanels of the bag, said face panels respectively including opposed edgeportions provided by said severed second thickened area, folding each ofsaid opposed edge portions along and substantially centrally of itslength'and attaching the same to its said respective face panel toprovide complementary tubular herns at said mouth end of the bag forreceiving a drawstring, and sealing said face panels together alonglongitudinally spaced apart transverse seal lines to form opposed sideedges of said bag.

References (Jilted in the file of this patent UNITED STATES PATENTS

1. THE METHOD OF MAKING A TUBULAR DRAWSTRING BAG, COMPRISING THE STEPSOF FORMING A SUBSTANTIALLY CYLINDRICAL TUBE OF THIN FLEXIBLE PLASTICMATERIAL HAVING A LOCALLY THICKENED AREA EXTENDING LONGITUDINALLYSUBSTANTIALLY ALONG ITS LENGTH, LONGITUDINALLY SEVERING SAID TUBESUBSTANTIALLY ALONG THE CENTERLINE OF SAID THICKENED AREA TO PROVIDE AMOUTH END AND OPPOSITELY DISPOSED FACE PANELS OF THE BAG, SAID FACEPANELS RESPECTIVELY INCLUDING OPPOSED EDGE PORTIONS PROVIDE BY SAIDSEVERED THICKENED AREA,